Mikro and I got an unexpected glimpse of hermit crab anatomy this week when our larger hermit crab, Coney (aka Coney Island Mermaid Parade Mercrab), molted. He did not engage in the digging behavior we expected to cue us in to an imminent molt, though he did hide out in his half coconut shell "hermie hut" for several days before the big day. Surprisingly, to us anyway, he chose to molt out in the open. He did not re-home himself to a larger shell; he just got rid of his too small exoskeleton and moved back in to the same old shell.
You can only tell so much about hermit crab anatomy from the molted exoskeleton. For example, there is a large, unprotected abdomen that isn't represented since the exoskeleton doesn't cover it.
For a much more comprehensive look at the anatomy of these fascinating creatures, please visit The Hermit Crab Patch.
Coney is back to hiding in his hut while his new exoskeleton hardens. Our littler crab, Curiosity's Manic on Monday Mars Rover, aka Curiosity) is taking full advantage and is much more active in exploring their shared habitat now that the big guy is otherwise occupied. We got Curiosity about 2 weeks ago, because hermit crabs are social and enjoy company.